First trimester · Week 13 of pregnancy
13 weeks pregnant: body, feeding, and care
The fetus can put a thumb in its mouth, vocal cords are forming, and the head is now about half the body's length. The first trimester closes.
Body and care — week 13
The fetus can put a thumb in its mouth, vocal cords are forming, and the head is now about half the body's length. The first trimester closes. Development notes on this page are general education summarized from ACOG patient-education material; they describe typical development, not your pregnancy specifically. Anatomy and growth are confirmed by your own provider and ultrasounds.
This week's checklist
- Note one body question — sleep, appetite, movement, comfort — and bring it to your next prenatal visit rather than searching it at 3 AM.
- Keep prenatal appointments on the schedule your provider sets; bring your questions list.
- Anything that worries you — bleeding, pain, reduced movement later in pregnancy — goes to your provider or urgent care first, never to a website.
Week 13 questions
What is happening at 13 weeks pregnant?
The fetus can put a thumb in its mouth, vocal cords are forming, and the head is now about half the body's length. The first trimester closes.
Which trimester is week 13?
Week 13 falls in the first trimester (weeks 1–13). See the first trimester hub.
How is a due date calculated?
A due date is typically estimated as 280 days (40 weeks) from the first day of the last menstrual period. It is an estimate — try the client-side due-date calculator; your provider's dating outranks it.
Educational information only — not medical advice. Every pregnancy and every baby develops on their own timeline. If you have any concern, talk to your obstetric provider or your baby's pediatrician.